Looking Good, Feeling Good: From the Inside Out
sponsoring Institutes
Main Getting Started Teacher's Guide Student Activities About NIH and NIAMS
glossary | map | contact 
National Institute of Arthritis and Musculoskeletal and Skin Disorders (NIAMS) website National Institutes of Health website

 

National Institutes of Health
National Institute of Arthritis and Musculoskeletal and Skin Disorders

Looking Good, Feeling Good: From the Inside Out

Main    Getting Started    Teacher's Guide    Student Activities    About NIH and NIAMS

Glossary    Map    Contact

Teacher's Guide hand using a mouse

Teacher's Guide

Lesson 4—Explore/Explain

Use It or Lose It

At a Glance

Overview

Lesson 4 introduces students to one behavior influencing muscle: resistance training. Students look at data from a laboratory study of the effects of resistance training on the muscle mass of rats. Students learn that laboratory animals, such as rats, are used as model systems in research. Students graph data that show an increase in muscle mass in response to resistance training and a decrease after training stops. Through analysis of data and class discussion, students learn that resistance training is an important influence on muscle mass.

Major Concepts

Objectives

After completing this lesson, students will be able to

Teacher Background

See the following sections in Information about the Musculoskeletal and Skin Systems:

  1. 2 Misconceptions about the Musculoskeletal and Skin Systems
  2. 4.2 Muscle
  3. 7 Influences

In Advance

Web-Based Activities
Activity Web Component? Photocopies Materials
1 No Master 4.1, Rat Resistance Training Study, 1 copy per team of 2
Master 4.2, Muscle Data, 1 transparency
Master 4.3, Graph Template, 1 copy per team of 2
Masters 4.4a and b, Resistance Training Study Worksheet and Graph Template, 1 copy per team of 2
None except photocopies and transparencies

Preparation

Prepare photocopies and transparencies.

Note to teachers: The study described in this activity is based on actual research by S. Lee and R.P. Farrar (see References section, number 27). The data we used are authentic, although in some cases, numbers were rounded off to make them easier to work with.

Procedure

  1. Ask students what the statement “use it or lose it” means. Then ask whether they think this statement is true.

Many students will recognize that the statement refers to using muscles and that if you do not regularly use your muscles, your muscles will get smaller; that is, you will lose muscle. Students are likely to think that the statement is true. Some students may have experienced (directly or indirectly through a sibling or friend) getting bigger muscles while training for a sport and then noticing the muscles “shrink” once the athletic season is over. Other students will have had experience with lose it from a limb being immobilized in a cast. After the cast is removed, the limb appears smaller (that is, has less muscle mass) than before the accident.

  1. Ask students how they could test this statement.

To test use it, students might suggest measuring arm or leg size before beginning an exercise program and again after exercising for a specified length of time. To test lose it, students might suggest measuring arm or leg size of an athlete during his or her athletic season and then again after the season has ended and training has stopped, or before and after a cast is placed on a limb. Encourage students to think about the limitations of their proposed tests. For example, is measuring an arm or leg an accurate measure of muscle size or mass (arms and legs contain fat, skin, and blood vessels in addition to muscle)? Students should also consider the variables that they might need to control, such as weight gain or loss and the type and duration of exercise.

  1. Divide students into teams of two and explain that they will look at the results of a study that investigated the effect of resistance training on rat muscle systems.
National Science Education Standards icon
Content Standard G:
It is part of scientific inquiry to evaluate the results of scientific investigation.
  1. Distribute one copy of Master 4.1, Rat Resistance Training Study, to each team. Instruct students to read the description of the research study.

Circulate and ensure that students understand the description of the study and what resistance training and stopping training are. You might ask students to explain what they think the study investigated. Encourage students to think about examples of resistance training that they or people they know take part in and examples of stopping training, such as football players stopping weight lifting after the season is over.

Note to teachers: To measure muscle mass, rats were euthanized, and the flexor hallucis longus muscle was removed and its mass was measured. Only one control group was used in this study because scientists in earlier studies, as well as this one, confirmed that the size of the animals does not change significantly during the 16 weeks of this type of experiment. Using one control group also reduces the number of animals that need to be euthanized.

  1. In this study, the experimental subjects are laboratory rats. We are interested in how muscles work in humans. Ask students to propose reasons why scientists use laboratory animals in research instead of people.

Scientists use animals in research to learn something about human biology. The animals serve as model systems for the human body. See the section Animals as Research Models in Implementing the Module.

Some students may object to working with laboratory animals. Refer to the advice given in How Can Controversial Topics Be Handled in the Classroom?. You may want to provide some examples of the many beneficial outcomes from experimentation involving laboratory animals. The benefits include the discovery of the causes of, the prevention of, and effective treatments for many infectious diseases, as well as the development and perfection of surgical techniques. For example, Louis Pasteur used rabbits and guinea pigs to identify the bacteria that cause anthrax and to develop a vaccine against this disease. Successful open-heart surgery and organ transplants are based on years of animal experimentation. Using animals in research studies of the musculoskeletal system has potential benefits for, among other things, improved rehabilitation following injury or disease.

  1. Refocus attention on the study description. Ask students to identify which groups in the study represent use it and which groups represent lose it. Then ask students to predict how muscle mass will compare for the control and each training group. (Will it increase, decrease, or stay the same?)

Group 1 represents use it and Groups 2 and 3 represent lose it. Accept all student responses at this point; they will discuss the use it or lose it statement in more detail at the end of this lesson.

Students are likely to predict that the muscle mass of rats from Groups 1, 2, and 3 that experienced resistance training will be larger than the muscle mass of the control rats. Many students may be unsure about the effect of stopping training on the muscle mass of rats and may think that Groups 1, 2, and 3 will have similar muscle masses.

  1. Display a transparency of Master 4.2, Muscle Data. Cover the data from Groups 2 and 3. Allow students to only see the control group and Group 1 data.
  2. Give each team one copy of Master 4.3, Graph Template. Instruct the teams to plot on the graph template the data from the control group and Group 1. Students should plot the data for this activity as a bar graph.

Encourage students to divide up the work of plotting the data. One student can plot the control and Group 1 data in this step. The other student can plot the Groups 2 and 3 data in the next step.

  1. Ask students to predict where the bars for Groups 2 and 3 will be on their graph. Then show students the remaining data on Master 4.2 and instruct them to plot Group 2 and Group 3 data on the graph template.

Student graphs should look similar to Figure 4.2.

Figure 4.2
Figure 4.2. Average mass of flexor hallucis longus (FHL) muscle for study groups.

  1. Give each team one copy of Master 4.4, Resistance Training Study Worksheet and Graph Template.
  2. Instruct teams to complete the worksheet and plot the values on the graph.

Continue to display a transparency of Master 4.2, Muscle Data, to provide students with the data they will need to complete the worksheet and graph. Students may not understand why it is important to plot the data again as a percentage of muscle mass increase. Explain that the percentages are useful for making comparisons. Student graphs should look similar to Figure 4.3.

Figure 4.3
Figure 4.3. Percent muscle mass increase of training groups over control group.

  1. Ask students if they think rats were a good model system in the study presented in this lesson. Encourage students to explain their responses.

Students are likely to respond that the rats in the study were a good model system. Students recognize that if they lift weights, their muscles will get bigger, and in this study the leg muscle of the trained rats also got bigger. Explain to students that this study is also a good model system because the training program of the rats is similar to how people train with weights. Like the training program in this rat study, human training programs usually involve training two to three times per week while gradually increasing the weight. Also explain to students that the increase in rat leg muscle mass is similar to the increase of muscle mass of humans in a resistance training program.

  1. Facilitate a class discussion of the students’ predictions about what use it or lose it means compared with the data from the study.

Most students probably recognize that training would increase the muscle mass. However, many students may be surprised by how much muscle mass decreased in the groups that stopped training.

Note to teachers: Students may believe that the numbers of muscle cells in the rats are changing during the study. Actually, the gain of muscle mass seen after resistance training and muscle mass loss after training stops is due to changes in the sizes of the muscle cells, not their numbers.

assessment icon
Assessment:
Assign Step 14 as homework and use it as an assessment of student learning for the lesson.
  1. Instruct students to individually write a short summary (two to four sentences) about what use it or lose it means to them after completing this lesson. Remind students to use what they learned from the resistance training study and the class discussions.

The following is an example of what a student might write: “Use it or lose it means that to maintain your muscles, you must use them by exercising or training. If you stop exercising or training, your muscle mass will decrease and you will lose muscle.”

Lesson 4 Organizer
Activity 1: Use It or Lose It
What the Teacher Does Procedure Reference

Ask the students what the statement “use it or lose it” means.

  • Do they think it is true?
  • How could they test it?
Steps 1 and 2

Divide the class into teams of two. Explain that they will examine the results of a study that investigated the effect of resistance training on rats.

Step 3

Give each team one copy of Master 4.1, Rat Resistance Training Study, and instruct students to read it.

master iconStep 4

Ask the teams why the study uses rats instead of humans.

Step 5

Ask the teams which groups represent use it and which groups represent lose it.

  • Instruct teams to predict how the muscle mass will compare for the control group and each training group.
Step 6

Display a transparency of Master 4.2, Muscle Data. Cover the data from Groups 2 and 3 so that only data from the control group and Group 1 are visible.

transparency iconStep 7

Give each team one copy of Master 4.3, Graph Template. Instruct the teams to plot the data from the control group and Group 1 as a bar graph.

master iconStep 8

Ask students to predict where on the graph data from Groups 2 and 3 will appear.

  • Reveal the remaining data on the transparency of Master 4.2, Muscle Data.
  • Instruct teams to plot the data on Master 4.3, Graph Template.
Step 9

Give each team one copy of Master 4.4, Resistance Training Worksheet and Graph Template.

  • Instruct teams to complete the worksheet and plot the values on the graph.
master iconSteps 10 and 11

Ask the students if they think rats were a good model for this study. They should explain their reasoning.

Step 12

Facilitate a class discussion about the students’ predictions regarding use it or lose it. Relate it to data from the study.

Step 13

Instruct students to individually write a short summary of what use it or lose it means to them now.

Step 14
master icon= Involves copying a master.
transparency icon= Involves making a transparency.

Return to Lesson Plans